As MOS transistors are scaled to the sub-quarter micron regime, the lateral distribution of dopants along the channel becomes a critical factor affecting their operation and performance. A technique that allows one to obtain the lateral doping profile is therefore indispensable. Vertical profiling techniques such as the C-V and SIMS have widely been used. The vertical C-V methods assumes a uniform lateral doping of channel and substrate regions, while the SIMS method is not feasible for submicron channel lengths. Lateral techniques for small size transistors, however, have met with less success. N. Khalil et al. in IEEE EDL-16(1), G. J. L. Ouwerling in Solid State Electronics., vol 34, p. 197, 1991 and Lee et al. in IEDM'97 Proceedings teach inverse modeling approach techniques by finding a lateral doping profile using an iterative procedure. Basically, these approaches determine whether the C-V/I-V characteristics of an assumed lateral doping profile matches the measured C-V/I-V characteristics of a device under test. However, none of these approaches teach, suggest, nor motivate how to accurately extract lateral doping profile directly from the measured data of the device under test.
Accordingly a need is seen to exist for a method for determining the non-uniform lateral surface doping for sub-micron CMOS devices directly from C-V measurements of the device, which is simple, nondestructive and accurate.